go: add «162. Find Peak Element»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/find-peak-element.go

@@ -0,0 +1,31 @@
+package main
+
+func findPeakElement(nums []int) int {
+	length := len(nums)
+
+	check := func(i int) bool {
+		return (i == 0 || nums[i-1] < nums[i]) && (i == length-1 || nums[i] > nums[i+1])
+	}
+
+	if check(0) {
+		return 0
+	} else if check(length - 1) {
+		return length - 1
+	}
+
+	left, right := 1, length-2
+
+	for left <= right {
+		mid := (left + right) / 2
+
+		if check(mid) {
+			return mid
+		} else if nums[mid] < nums[mid-1] {
+			right = mid - 1
+		} else if nums[mid] < nums[mid+1] {
+			left = mid + 1
+		}
+	}
+
+	panic("unreachable: peak element is guaranteed")
+}